A novel diagnostic is proposed to characterize the maturity of soot particles in a laminar axisymmetric coflow ethylene diffusion flame in terms of the spectral dependence of soot absorption function. The method relies on the combination of line-of-sight attenuation (LOSA) and emission measurements at four wavelengths (500, 532, 660 and 810 nm). The analysis of the measured signals enables the determination of soot temperature, soot volume fraction, soot maturity and the contribution of soot scattering to extinction. The analysis of extinction and emission measurements considers the spatial variation of soot optical properties. The introduction of a maturity index allows the evaluation of soot maturity based on the spectral variation of the soot absorption function. The maturity index is correlated with the organic or the mature soot content and finally in terms of the absolute value of absorption function at 810 nm. The methodology is validated using a set of synthetic spectral LOSA and emission signals representing experimental measurements based on numerical results obtained using the CoFlame code. A sensitivity analysis of the Abel inversion is also performed to properly address the effect of deconvolution procedure. Finally, the proposed method is applied to analyze the experimental data of spectrally-resolved LOSA and emission acquired in a laminar axisymmetric coflow ethylene diffusion flame established on a Gülder burner. The two-dimensional distributions of soot temperature, soot volume fraction, soot maturity, and the ratio of total scattering to absorption are determined. Mature soot particles are found on the top of the flame in the centerline region and also in the outer edge of the flame wing displaying strong gradients.

提出了一种新颖的诊断方法，以烟尘吸收功能的光谱依赖性来表征层状轴对称同流乙烯扩散火焰中烟尘颗粒的成熟度。该方法依赖于视距衰减（LOSA）和在四个波长（500、532、660和810 nm）处的发射测量的组合。对所测量信号的分析使得能够确定烟灰温度，烟灰体积分数，烟灰成熟度以及烟灰散射对消光的贡献。消光和发射测量的分析考虑了烟灰光学特性的空间变化。成熟度指数的引入允许基于烟灰吸收函数的光谱变化来评估烟灰成熟度。成熟指数与有机或成熟烟灰含量相关，最后与810 nm处的吸收函数绝对值相关。基于使用CoFlame代码获得的数值结果，使用一组合成光谱LOSA和代表实验测量值的发射信号对方法进行了验证。还对Abel反演进行了敏感性分析，以正确解决反卷积过程的影响。最后，将所提出的方法用于分析在Gülder燃烧器上建立的层状轴对称同流乙烯扩散火焰中的光谱分辨LOSA和发射的实验数据。确定烟灰温度，烟灰体积分数，烟灰成熟度以及总散射与吸收之比的二维分布。